Dual-pressure compressed gas circuit breaker with a downstream blast valve cooperative with interrupter housing in defining high-pressure region and with spaced breaker terminal disposed within said high-pressure region



O United States Patent 11113,546,408

[72] Inventors William II. Fhcher [56] References Cited Penn HillsPittsburgh; UNITED STATES PATENTS 3,214,542 10/1965 Yeckley etal.200/145 [21] P 539,407 3,271,548 9/1966 Kesselring 200/148(A) [2213,435,166 3/1969 Barkan 200/148 [45] Patented Dec. 8,1970 I [73]Assignee Westinghouse Electric Corporation Primary Examm"R0bel1 MaconPittsburgh p Attorneys-A. T. Stratton, C. L. McHale and W. R. Crout acorporation of Pennsylvania I ABSTRACT: A double-flow, two-pressurecircuit interrupter [54] DUAL'PRESSURE COMPRESSED GAS CIRCUIT of thedownstream valve type is mounted inside of and insu- BREAKER WITH ADOWNSTREAM BLAST VALVE lated from a metal tank contammg an Interruptingmedium at COOPERATIVE WITH INTERRUPTER HOUSING a relatively lowpressure. The interrupter is enclosed in an m- IN DEFINING HIGH-PRESSUREREGION AND sulatmg housing containing the medium at a high pressure.WITII SPACED BREAKER TERMINAL DISPOSED mum PRESSURE REGION Thecontinuous current path 1s through retractable contact WITHIN SA ibridging fingers which bridge a slidable movable arcing con- Chins 7Draw tact. During an interruption, downstream valves and the con- [52]0.8. CI. 200/148, tact bridging fingers are opened first, then theslidable mova- 200/145, 335/19 ble arcing contact is timed by asynchronous control device to [51] Ill. CL l'l0lh 33/86 open slightlybefore a current zero. The slidable movable arc- [50] Field ofSearch200/148, ing contact is driven by a mechanical energy storage HIGHPRESSURE CONTACTS PARTLY OPEN ARCING) CON T OL mechanism.

PATENIEDHEC 8i976 SHEET 1 OF 4 3.546408 I RELATWELY LOW PRESSURE &

22 |2 24 22 I ll 20 s g E /23 20 f I I I1 1 5 FIG. IA

FIG. 4 F36. I

INVENTORS WITNESSES William H. Fischer& MMWW Robert G.Colclcser, Jr.

PATENTEDUEC 8597B SHEET 3 OF 4 354540 6528 mnozomzuiw m N wzaodwm 2 mum$585K I21 DUAL-PRESSURE COMPRESSED GAS CIRCUIT BREAKER WITH A DOWNSTREAMBLAST VALVE COOPERATIVE WITH IN TERRUPTER HOUSING IN DEFININGHIGH-PRESSURE REGION AND WITH .SPACED BREAKER TERMINAL DISPOSED WITHINSAID HIGH-PRESSURE REGION This invention relates, generally, to circuitbreakers and, more particularly, to circuit breakers of the synchronoustype which have their arcing contacts opened just prior to a currentzero of an alternating current wave.

Most of the synchronous circuit breakers described in prior patentapplications have been of relatively low-power ratings and have not beensuitable for relatively high voltage service. An object of thisinvention is to provide a synchronous breaker suitable for 69 kv., 5,000mva. service.

Another object of the invention is to provide a circuit breaker which isrelatively small in size, low in weight, and which has a relatively highinterrupting rating.

A further object of the invention is to provide a doubleflow, downstreamvalve, gas-blast circuit interrupter for a circuit breaker of thedual-pressure type.

Still another object of the invention is to provide a circuitinterrupter having a low-moving mass and a short stroke, thereby makingit suitable for synchronous operation.

A still further object of the invention is provide contact means forbridging the synchronous arcing contact member of a circuit interrupter.

Another object of the invention is to provide for sequential operationof the synchronous arcing contact member and the bridging contact means.

A further object of the invention is to provide for opening thedownstream valves and the bridging contact means simultaneously, butclosing the valves independently of the bridging contact means.

Other objects of the invention will be explained fully hereinafter orwill be apparent to those skilled in the art.

In accordance with one embodiment of the invention, a double-flow,two-pressure circuit interrupter of the downstram-valve type is mountedinside of and insulated from a metal tank which is at ground potential.The interrupter is enclosed in an insulating housing containing aninterrupting medium, such as SP gas, at a relatively high pressure. Theouter tank contains the interrupting medium at a relatively lowpressure. The continuous current path is through retractable contactfingers which bridge a slidable moving arcing contact. During aninterruption, downstream valves and the contactbridging fingers areopened first, then the slidable moveable arcing contact is timed byasynchronous control device to open slightly before a current zero. Thevalves are reclosed shortly-after interruption takes place. During aclosing operation, the slidable arcing'contact closes first after whichthe retractable fingers close. The slidable arcing contact is driven bya mechanical energy storage mechanism. The retractable bridging contactfingers are opened by the same device that operates the valves.

For a better understanding of the nature and objects of the invention,reference may be had to the following detailed description, taken inconjunction with the accompanying drawings, in which:

FIG. I is a view, partly in elevation and partly in section, of acircuit breaker embodying features of the invention;

FIG. 1A is a detail fragmentary view looking in the direction of arrow Ain FIG. 1;

FIG. 2 is a diagrammatic view of the interrupter, its operatingmechanism and control system utilized in the circuit breaker showninFIG. 1, the interrupter being a partly open arcing position;

FIG. 3 is a graphical view showing the relation of the cur- 'rentsandtheflux in the synchronous control device utilized in the control systemshown in FIG. 2;

FIG. 4 is a detail view of an alternate method of supporting theinterrupter inside the breaker tank, and,

FIGS. 5 and 6 are views, similar to FIG. 2, showing the interrupter inthe. fully closed. position and the fully contact-open arcing position,respectively.

A single pole-unit of a circuit breaker embodying the present inventionis shown in FIG. 1 of the drawings. Additional pole-units, similar tothe one shown, may be utilized to provide a multipole breaker. Thestructure shown in FIG. 1 comprises a generally cylindrical metal ,tank11 supported by a metal framework 12, a circuit interrupter 13, anoperating mechanism and compressor unit 14, porcelain weather casings 15and 16, which insulate power conductors L1 and L2, respectively, fromthe tank 11, and current transformers 17, which may be mounted at eitherend of the tank 11.

The interrupter 13 is supported inside the tank 11, which is at groundpotential, by means of insulating support rods 18 attached to the end ofthe tank 11 and to the interrupter housing 19 in the manner shown. Acontrol unit and mechanical energy storing mechanism 21 is located atone end of the inter rupter unit 13. The metal tank 11 has a closedbottom cylinder 11a welded to it. The joint between 11 and 11a is wellrounded to reduce voltage stress gradient. An insulating operating rod22 extends from the mechanism housing 14 to the control unit 21. The rod22 may be in two sections joined through a rotatable shaft 20 whichextends through the side of the cylinder 11a. The tank 11 and thecylinder 11a contain an interrupting medium, such as air, or preferablySF, gas, at a relatively low pressure. A portion of the interrupter unit13 contains the interrupting medium at a relatively high pressure.Insulating feed pipes 23 and 24 connect the tank 11 and the interrupterunit 13, respectively, with the compressor in the mechanism andcompressor unit 14. The gaseous interrupting medium is withdrawn fromthe bottom of the cylinder 11a through the pipe 23', filtered andcompressed, and returned to the interrupter 13 through the pipe 24. Asshown in FIG. 4, the interrupter unit 13 and the mechanism 21 may besupported by an insulating tube 18a which extends into the cylinder 11aand is attached to the cylinder by a U-shaped ring 18b.

The mechanical energy storage mechanism 21 may be generally of the typedescribed in a copending U.S. Pat. application (Case No. 36,125) Ser.No, 369,208, filed May 21, 1964, now U.S. Pat. No. 3,284,732, issuedNov. 8, 1966 to Fritz Kesselring. However, it differs from the priormechanism in many respects. As shown more clearly in FIG. 2, themechanism comprises a flywheel 25 driven by a ratchet pawl 26, a clutchwheel 27 connected to the flywheel 25 by a shaft 28, and the operatingrod 22, which is actuated by a suitable actuator, such as a solenoid 30.An air piston and cylinder, or other suitable actuator, may be utilizedin place of the solenoid 30. The upper end of the rod 22 is connected toone arm of a bellcrank lever 31 pivotally mounted on a support 32. Theother arm of the lever 31 is connected by a link 33 to an arm 34, whichcarries the ratchet pawl 26. The arm 34 is rotatably mounted on theshaft 28. When the rod 22 is moved downwardly by the solenoid 30, thepawl 26 engages teeth 35 on the flywheel 25 to drive the wheel in aclockwise direction. The rod 22 is biased upwardly by a spring 36, whichengages the one arm of the lever 31.

As also shown in FIG. 2, the housing 19 for the interrupter unit 13 isgenerally cylindrical in shape, and is composed of a suitable insulatingmaterial. Two generally round terminals 41 and 42 are disposed insidethe housing 19 in spaced relation. The terminal 41 has an annular flange43 thereon, and the terminal 42 has an annular flange 44 thereon, whichengage the inner wall of the housing 19 to retain the interruptingmedium in a space 45 between the terminals at a relatively highpressure. As explained hereinbefore, the interrupting medium is suppliedto the region 45 between the terminals through the feed pipe 24. Theterminal 41 has a generally Y-shaped opening 46 therethrough, and theterminal 42 has a generally Y- shaped opening 47 therethrough. As shownby the dashed lines 48a, a valve 48 closes the arms of the opening 46 toprevent the medium from flowing through the opening when the valve 48 isclosed. Likewise, a valve 49 closes the arms of the Y-shaped opening 47,as shown in FIG. 5, to prevent the medium from flowing through thisopening when the valve 49 is closed.

A hollow movable arcing contact 51 is slidably disposed in the leg ofthe Y-shaped opening 47 and, as shown by the dashed lines 51a in FIG. 2,extends into the leg of the Y- shaped opening 46 to engage spring biasedcontact fingers 52 mounted in the terminal 41, thereby electricallyconnecting the terminals 41 and 42 when the arcing contact 51 is in theclosed position, as shown in FIG. 5. The contact 51 is actuated by anoperating rod 53 which is reciprocated by the storedenergy mechanism 21,as will be described more fully hereinafter. The rod 53 is engaged bycontact fingers 54 provided on a portion 55 of the terminal 42. Thevalve 49 is slidably disposed on the terminal portion 55. Likewise, thevalve 48 is slidably disposed on a portion 56 of the terminal 41. Thevalves 48 and 49 are operated in a manner described more fullyhereinafter.

In order to reduce the size and the mass of the movable arcing contact51, a main current path through the interrupter is provided throughretractable contact bridging fingers 57, which are pivotally mounted inrecesses 58 in the terminal 42.

, As shown in FIG. 5, the fingers 57 engage a projection 59 on terminalsat a relatively high pressure when the breaker is open. Thus, thedistance between the terminals 41, 42 may be relatively small.

As shown in FIG. 2, the linkage of the interrupter is in the partly openposition of the circuit breaker showing the arcing condition. In thebreaker-closed position, shown in FIG. 5, the movable contact 51 engagesthe contact fingers 52. The retractable contact fingers 57.engage theportion 59 of the terminal 41. The valves 48 and 49 are in the positionshown by the full lines in FIG. 5, thereby sealing off the high-pressureinterrupting medium in the region 45, from the low-pressure medium intank 11. A spring-biased detent 61 is in a notch 62 in the shaft 53,thereby holding the movable contact 51 closed, as shown in FIG. 5. Aspreviously explained, the bridging fingers 57 are the maincurrent-carrying fingers.

When the current in the conductor L2 exceeds a predetermined amountbecause of a fault condition, a relay 63 is energized by a currenttransformer 64. Contact members 65 of the relay are closed to energizethe solenoid 30 through normallyclosed contact members 66 on thesolenoid, as shown in FIG. 5. The operating rod 22 is then moveddownwardly to drive the flywheel 25 and the clutch wheel 27 clockwisethrough the ratchet 26, as previously explained. At the same time thelever 31 drives a pair of links 67 to the right, which, in turn, drivelinks 68 to the right to operate bellcrank levers 69, therebydisengaging the contact bridging fingers 57 from the surface 59 to openthe bridging circuit through these fingers, as shown in FIG. 2. Themovable contact 51 now carries the full current as shown in FIG. 2. Thelinks 68 also drive latches 71 to the right, thereby opening blastvalves 49 and 48 to permit the interrupting medium to flow from thehigh-pressure region 45 to a low-pressure region through the Y-shapedopenings in the terminals 41 and 42, as shown in FIG. 2. The valve 48 isconnected to the valve 49 through an insulating rod 72, a lever 73 andlinks 74.

When a trip solenoid 75 is energized, it drives a dog 76counterclockwise by means of a lever 76a to engage a V- groove 77 in theclutch flywheel 27. The head of the dog 76 is shaped to fit into theV-shaped groove 77 and frictionally engage the sides of the rotatinggroove. The dog 76 is carried by an arm 78 rotatably mounted on theshaft 28. The arcing con tact 51 is now driven to the right or openposition through a link 79 and a lever 81 pivoted at 82. This is timedby a synchronous control device 83 to occur I to 2 milliseconds before acurrent zero. When the contact 51 moves to the full open position, asshown in FIG. 6, a detent 61 moves into a notch 84, thereby holding thearcing contact 51 in the open position. The current is interrupted atcurrent zero.

The latches 71 are disengaged from the blast valve 49 when the latcheshit kickoff pins 85. This releases valves 48 and 49 allowing them toreclose under the action of a spring 86, thereby shutting off the flowof the interrupting medium. However, the reclosing of the valves 48 and49 is delayed a predetermined time by a dash-pot 87, or other suitabletimedelay device, to permit the current to be interrupted at a second orlater current zero in case it is not interrupted at the first currentzero, as will be explained more fully hereinafter.

Spring-biased latches 88 enter notches 89 in the links 68, therebyholding the contact gridging fingers 57 in the open position. The dog 76is released from the clutch 27 by a kickoff probe 91. The operating rod22 and associated linkage are reset by the spring 36. The rod 22 isshown in its reset position in FIG. 5 and in its actuated position inFIG. 6. The links 67 are free to reset, ormove to the left independentlyof the links 68. Thus, the valves 48 and 49 are opened simultaneouslywith the bridging contact fingers 57, but the valves are reclosedindependently of the bridging contact fingers. Furthermore, the openingof the blast valves and the retractable contact bridging fingers isdisassociated from the opening of the movable arcing contact 51. Thismeans that the mechanism driving the moving arcing contact can be madesmaller than would otherwise be possible.

The reclosing of the valves after an interruption conserves thehigh-pressure interrupting medium, and also permits the open-circuitvoltage to beheld across the terminals 41 and 42 through thehigh-pressure medium. The gas-flow paths through the terminals 41 and 42are shaped to give a region of high-velocity approach upstream andradial to the arc, and allow for expansion of the heated gas downstreamof the arc during an interruption. I

To start a closing sequence of the circuit breaker, a push button 92 isclosed, thereby energizing a solenoid to close a circuit through contactmembers 93 and normally closed contacts of antipumping relay to energizethe solenoid 30, and drive the operating rod 22 downwardly to rotate theflywheel 25 and the clutch wheel 27 clockwise in the manner previouslydescribed. The circuit through the solenoid 30 is interrupted by theopening of contacts 66 after a delayed time, and the rod 22 andassociated linkage reset under action of the spring 36. The relay 100 isenergized simultaneously with the solenoid 30 and remains energizeduntil the pushbutton is released, thereby preventing pumping of thesolenoid 30. The rod 22 now goes into overtravel in an upward directionwhich occurs only on a closing operation. Overtravel upwardly during atripping operation is prevented by a latch 94, which engages aprojection 95 on the rod 22. The latch 94 is biased to the closedposition by a spring 96, and is released by the solenoid 90 when it isactuated to close the contact members 93 to energize the solenoid 30, aspreviously described.

A projection 97 on the link 67 drives a pivoted lever 98counterclockwise to engage a dog 99 with the groove 77 in the clutchwheel 27 The dog 99 is carried by an arm 101 rotatably mounted on theshaft 28. The movable arcing contact 51 is driven to the left, or closedposition by a link 102 and a lever 103 pivoted at 104. Near the end ofthe stroke of the contact 51 a projection 105 engages the latches 88 torelease the latches, thereby permitting the bridging contact fingers 57to reclose, and the latches 71 to reset under the action of springs 106,which engage the levers 69. The links 67 are free to move to the leftindependently of the links 68, which actuate the bridging contactfingers 57, but engages the links 68 when they are moved to the right. Akickoff probe 107 releases the dog 99 from the clutch wheel 27. Aspreviously explained, the detent 61 enters the notch 62 to retain thearcing contact 51 in the closed position until it is opened in themanner hereinbefore described.

If the breaker should fail. to interrupt at the first current zero, thearcing contact 51 can be immediately reclosed by energizing a solenoid108 to actuate the lever 98 to engage the dog 99 with the clutch wheel27. The arcing contact 51 is then reopened just prior to a secondcurrent zero by energizing the solenoid 75. The energization of thesolenoids 108 and 75 is controlled by the synchronous control device 83.

One form of synchronous control device, which may be utilized isdescribed in a copending U.S. Pat. application Ser. No. 419,045, filedDec. 17, 1964, now U.S. Pat. No. 3,379,850, issued to F. A. Azinger, andassigned to the Westinghouse Electric Corporation. As described in theAzinger patent, the synchronous control device 83 comprises a saturatingcore 111 having a main airgap 112 and at least one other airgap 113therein. An armature coil 114 is disposed on an armature core 115rotatably mounted in the airgap 112. A contact arm 116 is carried by thearmature core 115. The conductor L2 is disposed on the core 111 toenergize the core by the current to be interrupted.

The operation of the synchronous device may be understood by referringto FIG. 3. As shown, the current 1,, which is the current to beinterrupted, sets up a flux B in the magnetic core 111. At t themagnetic circuit becomes saturated. At t,, the core 111 unsaturates whenthe current decreases below a predetermined amount, and the rapid rateof change in the flux B which takes place as the current 1 approacheszero induces a secondary current i; in the armature coil 114, whichreacts with the flux across the airgap 112 to produce a torque whichrotates the armature coil 114. This torque is in one direction from t,to but reverses as the current 1 passes through zero at since the flux Bis in the opposite direction while the current i continues to flow inthe same direction. The reversal of the torque reverses the directionof'rotation of the armature coil 114. The current drops to zero at 1when the magnetic core is saturated during the other half-cycle of thecurrent i At t, the core again unsaturates, and the current i is in theopposite direction and reacts with the flux B to produce a torque torotate the coil 114 andthe arm 116 in the original direction. The torquereverses when the current 1 passes through zero at t The current i dropsto zero at Thus, the contact arm 116 is oscillated back and forth.

The oscillation of the contact arm 116 is restrained by tension springs117 and 118 attached to the arm 116 at opposite sides of the armature.core 115. Thus, the contact arm 116 is prevented from engagingstationary contacts 121 and 122 or contacts 123 and 124 so long as thecurrent flowing in the conductor L2 is below a predetermined amount.However, when the current exceeds a predetermined amount, the arm, whichwill have been already in motion, can, because of the greater torqueavailable, overcome the spring loading and travel to meet a set ofstationary contacts, thereby causing the device 83 to function as asynchronous-current relay.

in the present system, the device 83 is utilized as a synchronous relayto initiate the-opening of the movable contact member 51. As explainedhereinbefore, this is done by energizing the solenoid 75. As shown, whenthe contact arm 116 bridges contacts 12land 122, a conductor 125 isenergized. The conductor 125 is connected to the solenoid 75 throughauxiliary contact members 126, actuated by the operating rod 53, and aconductor 127. The auxiliary contacts 126 are closed when the maincontact 51 is closed. The energization of the solenoid 75 effects theopening of the contact 51 in the manner hereinbefore described.

As explained hereinbefore, the device 83 is utilized to cause thecontact 51 to be immediately reclosed if the current is not interruptedat the first current zero. As previously explained,

the torque on the contact arm 116 reverses with each halfcyele of thealternating current wave. Thus, if flthe current is not interrupted atthe first current zero, the contact arm 116 bridges contacts 123 and 124to energize a conductor 128. The conductor 128 is connected to thesolenoid 108 through auxiliary contacts 129 and a conductor 131. Thecontacts 129 are actuated by the operating rod 53, and are closed whenthe main contact 51 is in the open position. After the main contact 51is reclosed, it is reopened just prior to the second current zero in thesame manner as it was opened prior to the first current zero. Thecontact 51 continues to reclose and reopen until the current isinterrupted.

The synchronous control device 83 controls the operation of the movingcontact 51. Control devices of other types may be utilized, if desired.Also, operating mechanisms of other types may be utilized.

If desired, the circuit breaker may be opened nonsynchronously byclosing a pushbutton 132 to energize a solenoid 130, thereby closing acircuit through contact members 133 to energize the solenoid 30 whichdrives the rod 22 downwardly to rotate the flywheel 25 and the clutchwheel 27 clockwise as previously described. Overtravel of the rod 22downwardly is now permitted since a latch 134 is moved to the left whereit will not engage a projection 135 on the rod 22. Normally, the latch134 is biased by a spring 136 to prevent downward overtravel by engagingthe projection 135. The downward overtravel of the rod 22 causes a probe67a on the lower link 67 to engage the lever 7611 which actuates the dog76 into engagement with the rotating clutch wheel 27, thereby openingthe breaker as previously described.

From the foregoing description it is apparent that the inventionprovides a circuit interrupter having a moving contact, which isrelatively low in mass and travels a relatively short distance. Thus,the operating mechanism for the moving contact can be made small sincethe operation of the main current carrying contact bridging fingers andthe valves is disassociated from the moving arcing contact. Thedouble-flow, downstream valve arrangement makes efficient use of theinterrupting medium. Maintaining the interrupting medium at a highpressure between the stationary terminals of the breaker, when thecontacts are in the open position, permits the distance between theterminals and between the contacts to be relatively small, therebyreducing the size of the interrupter, and, consequently, the overallsize of the circuit breaker. The breaker is of the dead tankconstruction. Conventional current transformers can be utilized with thebreaker.

Since numerous changes may be made in the above described constructionand different embodiments of the invention may be made without departingfrom the spirit and scope thereof, it is intended that all subjectmatter contained in the foregoing description, or shown in theaccompanying drawing shall be interpreted as illustrative, and not in alimiting sense.

We claim:

1. In a gas-blast circuit breaker, in combination, a metal tank forcontaining an interrupting gaseous medium at a relatively low pressure,an interrupter housing mounted inside of and insulated from the tank,terminals spaced inside the interrupter housing, a movable arcingcontact connecting said terminals, retractable contact means bridgingthe movable arcing contact when closed, valve means disposed within saidinterrupter housing and defining with the interrupter housing ahigh-pressure region, said terminals disposed within the highpressureregion, said valve means functioning as a downstream blast valve,actuating means for opening the bridging contact means and the valvemeans simultaneously, and additional actuating means for opening themovable arcing contact.

2. The combination defined in claim 1 including means for reclosing thevalve means independently of the bridging contact means.

3. The combination defined in claim 1 wherein the additional actuatingmeans opens the movable arcing contact after the opening of the movablebridging contact means and the valve means, and including control meansfor controlling the operation of the additional actuating means.

4. The combination defined in claim 1 wherein the additional actuatingmeans opens the movable arcing contact after the opening of the bridgingcontact means and the valve means, and including synchronous controlmeans for controlling the operation of the additional actuating means toopen the movable arcing contact a short time before a current zero of analternating current wave.

5. The combination defined in claim 4 wherein the synchronous controlmeans controls the operation of the additional actuating means toreclose the movable arcing contact if the current is not interrupted atthe current zero.

6. The combination defined in claim 1 wherein the terminals haveopenings therein and the movable arcing contact is movable in saidopenings to electrically connect the terminals, and the valve meanspermits the interrupting medium to flow through the openings whenopened.

7. The combination defined in claim 6 including means for reclosing thevalve means independently of the bridging contact means.

8. The combination defined in claim 1 wherein the additional actuatingmeans comprises mechanical energy storage means for opening the movablearcing contact after the opening of the contact bridging means and thevalve means, and including control means for controlling the operationof the mechanical energy storage means.

9. The combination defined in claim 8 wherein the control means is asynchronous control means for controlling the operation of themechanical energy storage means to open the movable arcing contact ashort time before a current zero of an alternating current wave.

10. The combination defined in claim 9 wherein the synchronous controlmeans controls the operation of the mechanical energy storagemeans toreclose and then reopen the movable arcing contact if the current is notinterrupted at the first current zero.

11. A circuit interrupter comprising a generally cylindrical insulatinghousing, two terminals disposed inside the housing in spaced relation toretain an interrupting medium between the terminals at a relatively highpressure, each terminal hav ing an opening therethrough, valve meanspreventing the medium from flowing through the openings, a movablearcing contact movable in said openings to connect the terminals,contact bridging means mounted on one terminal and engaging the otherterminal to bridge the movable arcing contact, actuating means foropening the contact bridging means and the valve means, and additionalactuating means for opening the movable arcing contact.

12. The circuit interrupter defined in claim 11 wherein the movablearcing contact is a hollow contact member, the contact bridging meansare pivotally mounted on one terminal and interrupt the bridging circuitwhen opened, the valve means permit the interrupting medium to flowthrough the opening and the hollow movable arcing contact member whenopened, and the hollow movable arcing contact member interrupts thecircuit through the interrupter when opened.

13. The circuit interrupter defined in claim 12 including control meansfor controlling the operation of the actuating means to cause themovable arcing contact member to p open after the opening of the contactbridging means and to close before the closing of the contact bridgingmeans.

14. The circuit interrupter defined in claim 11 wherein each terminalhas an annular flange thereon engaging the wall of the housing, eachterminal has a generally Y-shaped opening therethrough, the valve meansclose the arms of the openings to prevent the medium from flowingthrough the openings, the movable arcing contact is a hollow contactmember slidably disposed in the leg of one opening and engaging the legof the other opening to electrically connect the terminals, and thebridging contact means and the valve means are opened simultaneously tointerrupt the electrical bridging circuit and to permit the interruptingmedium to flow through the openings and the hollow arcing contactmember.

15. The circuit interrupter defined in claim 14 including means forreclosing the valve means independently of the contact bridging means.

16. The combination defined in claim 8 wherein the control means is anonsynchronous control means for controlling the operation of themechanical energy storage means to open the

